The present invention relates to the sector of combustible, inflammable and toxic gases present in the air, more particularly generated by leaks of pipes, for instance leaks of gaseous hydrocarbons or evaporation of potentially toxic and/or explosive gases. For instance a sector of interest for the present invention is the environmental detection of gases, more particularly for protection and safety of the operators of drilling, extraction, transport and stocking plants. Particular examples of hazardous environments certainly are oil processing places, such as rigs and/or gas extraction places or with high risk of presence of toxic or flammable gases, also produced by many industrial processes. Places of interest for the present invention are first of all drilling and lifting sea plants such as offshore rigs, and land plants like oil wells, where a possible gas escape contains a mixture consisting of flammable and toxic gases, more particularly H2S (hydrogen sulphide) which is extremely toxic even at very low concentration. This may happen also in chemical and petrochemical plants, in industries for transforming and stocking liquid and gaseous hydrocarbons or industries for conversion in other fuels such as hydrogen, ammonia and others.
Still of interest for the detection devices which will be hereinafter illustrated according to the present invention, is the detection of products converted as fuels containing toxic gases also in the liquid phase, which may release combustible and/or toxic gases, even at room temperature. Gases to be detected according to the present invention, for instance released in the atmosphere, may endanger in a particularly dangerous way the life of operators, and cause explosions as well, notwithstanding the existence of steady checks and safety measures, such as alarms and compulsory protective means, which unfortunately often result to be insufficient.
The present invention relates to innovative systems for detecting toxic or explosive gases, also comprising possible detecting and measuring devices for said systems. More particularly, the detection devices and systems proposed by the present invention are designed to solve the most serious and unfortunately well known problems of the prior art detection devices. More particularly, generally the detection systems available on the market for combustible and toxic gases for fixed installations, comprise only one kind of gas sensor for one detection technology only. Each sensor of this kind is generally connected to a single electronic transmitter. More particularly, this single channel detection aspect may possibly require presence of more detectors and in the best case this would anyway involve an increase of costs. In the worst case of one detector for a single gas, either because only one gas is indeed present in the environment or the possible arrangement of two detectors in the same room was not correctly done, the problems that may occur could be much more serious. Indeed, in case two or more gases are present in an area and the detectors are not correctly positioned (or two different kinds of detectors are not present), so that the presence of said two gases contemporaneously in the same area is not detected, in case of escape of one or more toxic and flammable gases, which individually would have only limited dangerous consequences, but when being together in the same environment, could produce toxic and even explosive mixtures, if said gases are not detected, the effects could be not only dangerous, but even devastating for persons and places, as known from news of explosions in factories and/or poisoning of individuals and the frequent fires and explosions of offshore rigs and land wells.
Moreover, a definitely considerable proportion of gas detectors available on the market have big problems due to the so-called fouling and clogging of the gas inlet filter of the sensor. This fouling problem involves false or even absent detections. This effect cannot be detected in sensors of the state of the art technology, because the filter is a component integral with the sensor body and this clogging status may be detected only with physical calibration text with sample gas. The experts in this field are aware that the possible use of compressed air to clear the filter, would only damage the sensitive element disposed after the filter. The sensor clogging drastically reduces the sensor response time, usually occurring by diffusion exploiting the gas partial pressures inside and outside the sensor. The sensor response time is certainly a factor of greater relevance for the timely recognition of possible dangers; clogging of filter is progressive as a function of the environment and it is definitely very onerous for applications on or near the sea, where salt deposit is a true hazard, because the sensor is prevented to alert the existence of danger, that as a rule requires an immediate and timely communication.
On the other hand clogging of filters often occurs in a very short time, and therefore this is still more dangerous for the correct operation of the detectors, more particularly but not exclusively on offshore rigs and in desert areas, where it frequently occurs that a sintered filter gets clogged by salt, fine powder or polluting agents also generating particulates in industrial areas.
In addition, the widespread sensors presently available on the market, like those well known and used by the oil companies and others operative in the oil and gas sector, have a sensor body and a sintered filter integral with said body, to be used in areas classified and subject to possible generation of explosive mixtures. When said filter becomes clogged, and people becomes aware that the filter is clogged, which is not easy in view of the place where the filter is installed, for safety reasons the filter must be changed even when it is only 50% clogged. The replacement operation involves high operative costs because one must replace the entire sensor, with which the filter is integral. Once the response time of the sensor has been found to be outside the standard parameters, said sensor must be replaced with high costs and times.
An illustrative example of the hereinbefore mentioned prior art problems can be found in document US 2012/0192623 A1 disclosing a classic system of gas detection comprising use of several kinds of sensors, carrying out individual measurements for a single type of gas and showing on a display said single measurement. In any case the display can show only one measure data. Moreover the type of sensor disclosed is a fixed sensor with sintered filter, which as above discussed cannot be cleaned and replaced individually, but the detection sensor must be replaced entirely, which is a very expensive operation, as already pointed out. Still more seriously, this type of sensors is a great danger for safety in the places that the sensor should theoretically keep safe; indeed said filters may be fully clogged, without showing any malfunctioning evidence even in the calibration stage, and this does not allow to obtain reliable reading and monitoring operations concerning the presence and concentration of those gases that said sensors should be able to detect, with possible tragic consequences like those above cited as prior art problems.
Some examples of detection or sensitive elements used in this sector are disclosed in document EP 1544614 illustrating an element sensitive to two gases, comprising two electrodes separated by a gasproof portion, detecting in this device for example carbon monoxide and hydrogen sulphide. This disclosure is moot about the complete sensor or the detection methods, the filter cleaning and so on. These sensitive elements are adapted to use with a broad range of assembled sensors, but the final reliability of the sensor is not depending from these elements, although they are efficient detectors to be used as a part of a larger device.
In a similar point of view of sensitive elements used or usable in this sector, document WO 2011/053721 discloses an electrochemical sensitive element comprising at least a first and a second gas detection electrode which are kept totally separate from each other as to the detection and the subsequent diffusion of gases detected inside the system, as well as for the subsequent transmission and recognition of the substance. The essential factor of this disclosure is an anti-diffusion barrier, that seems to be an important factor in the indicated sector. However in the sector of detecting gas for explosion danger, this factor is not very important because the gases to be detected are unfortunately already present mutually mixed in the surrounding air. In any case these sensitive elements cannot be compared with the gas detection devices, namely autonomous apparatus processing and generating the situation of danger that may occur.
Document EP 1197753 discloses a portable device for gas detection that may be attached to the human body, comprising a standard gas detection sensor, nothing is being stated for the safety problem in connection with fouling of sensors and the other problems hereinbefore discussed.
An object of the present invention is to provide for a detection system solving the above cited problems.
More particularly, an object of the present invention is to provide for a detection system with at least a double channel, allowing the contemporaneous detection of two or more gases.
Another object of the present invention is to provide for a system where the filter cleaning operation results to be simple and quick, and said cleaning substantially does not interrupt the sensor function of detecting continuously the possible presence of the gas at the installation place.
Connected thereto, it is also an object of the present invention to provide for a detection system with replaceable filters, without requiring replacement of the entire sensor body.
It is a further object of the present invention to optimize the production costs and the related costs for the users.
An essential object of the present invention is to increase safety and reliability of detection of toxic or flammable gases, in all the above cited sectors as well as other sectors where said system may be needed for safety purposes.
It is also an object of the present invention to provide for a detection system which should be performing, reliable, simple to be used as well as economically advantageous.